Mechanical Properties of Blends of Low-Density Polyethylene with Chlorinated Polyethylene

The results of experimental investigation into the mechanical properties of blends of low-density polyethylene (LDPE) with chlorinated polyethylene (CPE) in tension are presented. The specimens of pure LDPE, CPE, and nine types of LDPE/CPE blends, with different content of components at 10 wt.% intervals, were examined. Data on the influence of blend composition on the tensile stress-strain diagram, elastic modulus, yield stress, breaking stress, and ultimate elongation are obtained. The results of investigations of creep are also reported. It is found that the creep compliance (the total current compliance minus the elastic compliance) obeys the power law of creep.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 3, pp. 391–404, May–June, 2005.     

Phase Structure of Polyamide 6/Poly(styrene-co-acrylonitrile) and Poly(styrene-b-(ethylene-co-butylene)-b-styrene) or Poly(maleated Styrene/Ethylene-co-Butylene/Styrene) Ternary Blends

Two sets of ternary blends; polyamide 6/poly(styrene-co-acrylonitrile)/poly(styrene-b-(ethylene-co-butylene)-b-styrene) (PA6/SAN/SEBS) and polyamide 6/poly(styrene-co-acrylonitrile)/poly(maleated styrene/ethylene-co-butylene/styrene) (PA6/SAN/SEBS-g-MA), based on 70 wt% of matrix and 30 wt% of the dispersed phases at various concentrations of the minor components, were prepared via melt blending. Morphologies of the ternary systems were studied using scanning electron microscopy (SEM) and compared with the predictions of the spreading coefficient (SC), minimum relative interfacial energy (RIE), and dynamic interfacial energy (DIE) phenomenological models. The effects of different reported surface tensions of the used polymers and different protocols of the core-shell ratio calculation on the prediction of the models were investigated. The core-shell structure for PA6/SAN/SEBS system and two separate minor phases for PA6/SAN/SEBS-g-MA were observed at all of the compositions. The results indicated that the most important parameter for the accurate prediction of the models is the accurate calculation of the interfacial tension of the used polymers, in both the static and dynamic conditions.     

涤棉混纺织物近红外定量分析模型的建立及相关问题探讨

在废旧纺织品回收再利用中,纤维类型和含量的快速、准确测定是回收方案的关键部分。以598个废旧涤棉混纺织物为研究对象,采用便携式近红外（NIR）光谱仪测试了样品的原始近红外光谱。在1 400～1 700和1 900～2 200 nm光谱区域,100％棉和100％聚酯样品的光谱存在明显差异,并且这些光谱差异存在于各种颜色纤维上。同时探讨了斜线光谱产生的原因可能是由于织物表面效果、着色方法及粘附在纤维表面的细小颗粒造成的。深色样品易造成其光谱基线在短波区发生漂移,经导数预处理后,基线漂移基本消除,斜线光谱呈现出正常光谱的特征。利用偏最小二乘（PLS）法结合一阶导数、S-G平滑、均值中心化和正交信号校正法,建立了废旧棉-涤混纺织物定量分析模型。为了验证模型的可靠性,选取346个样本采用内部交叉验证均方根误差（RMSECV）和预测样品集外部检验法对模型进行检验,模型的RMSECV值0.002、校正集相关系数R_C＝0.998、预测相关系数R_P=0.997、预测标准差SEP＝1.121,模型预测正确率可达97％。对模型进行匹配样本t检验结果显示,NIR方法与国家标准方法无显着性差异。NIR预测值与重量法测定值误差在±3％以内时,二者的一致性在90％以上,当误差在±5％以内,二者的一致性在95％以上,分析时间小于10 s。因此,利用近红外技术结合所建模型可以快速、准确地预测废旧棉/涤混纺织物纤维成分的含量。     

Characterizing domain mixing effects in hydrogen bond-compatibilized polymer blends

The nature and extent of phase mixing in blends of hydroxyl-functionalized polystyrene and poly(ethyl acrylate) (PS/PEA), where the driving force for mixing is hydrogen bonding, are characterized by several techniques. Small-angle x-ray scattering (SAXS) shows a reduction in average domain size with increasing functionalization level, a result also evident from scanning electron microscopy (SEM). Together, the two techniques reveal a very broad distribution of domain sizes. At high functionalization levels, both SAXS and SEM indicate a high degree of “in-domain” mixing, with little or no pure PS or PEA remaining in the blends. Mathematical modeling of dynamic mechanical thermal analysis (DMTA) data is employed to quantify this progression. Initially, mixing is primarily interfacial, but as the functionalization level increases, the mixed interphase rapidly grows to occupy the entire material. In agreement with the SAXS and SEM results, DMTA modeling shows that further increases in the functionalization level suppress the amplitude of composition variations in the sample. The onset of extensive in-domain mixing coincides with the marked changes in stress-strain behavior observed previously in these materials. © 1994 John Wiley & Sons, Inc.     

Emission properties of thin films of electroactive doped polymers

We have studied the effect of the intensity of the exciting radiation and the temperature on the emission properties of two kinds of thin-film samples based on blends of two types of organic electroactive materials: polyfluorene + iridium triphenylpyridinate and polyepoxypropylcarbazole + zero-th order PAMAM dendrimer with eosin. We have shown that an increase in the excitation intensity leads to an increase in the intensity of the luminescence of the polymer matrices and the iridium complex up to a power density of 300 kW/cm², and the emission of the dendrimer is rapidly saturated and does not return to the initial value when the excitation level decreases. Heating up to 170°C followed by cooling causes an increase in the intensity for all the components except the dendrimer. The data obtained show that annealing is an important method for improving the emission efficiency of the proposed thin-film structures, due to a change in the packing of the activator molecules in the polymer matrix leading to more efficient transfer of the excitation energy. Molecules of the studied dendrimer are not stable when exposed to optical radiation and temperature. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 820–825, November–December, 2007.     

Production of Mesoglycan/PCL Based Composites through Supercritical Impregnation

The development of targeted therapies for wound repair is knowing a growing interest due to the increasing aging of the population and the incidence of chronic pathologies, mainly pressure ulcers. Among molecules recruiting cell populations and promoting the formation of new vital tissue, sodium mesoglycan (MSG) has been proven to be effective in wound healing. In this work, MSG impregnation of polymer matrices has been attempted by a supercritical carbon dioxide-based process. Polymeric matrices are composed of polycaprolactone blends, where water-soluble polymers, polyethylene glycol, polyvinyl pyrrolidone, gelatin, and thermoplastic starch, have been employed to modulate the MSG release, making the devices potentially suitable for topical administrations. Two different techniques have been used to obtain the films: the first one is compression molding, producing compact and continuous structures, and the second one is electrospinning, producing membrane-like designs. A higher amount of MSG can be loaded into the polymeric matrix in the membrane-like structures since, in these films, the impregnation process is faster than in the case of compression molded films, where the carbon dioxide has firstly diffused and then released the active molecule. The type of water-soluble polymer influences the drug release rate: the blend polycaprolactone-gelatin gives a prolonged release potentially suitable for topical administration.     

Unique evolution of spatial and dynamic heterogeneities on the glass transition behavior of PVPh/PEO blends

Glass transition behavior of hydrogen bonded polymer blends of poly(vinyl phenol)(PVPh) and poly(ethylene oxide)(PEO) is systematically investigated using normal differential scanning calorimetry(DSC) and recently developed multifrequency temperature-modulated DSC(TOPEM),in combination with Fourier transform infrared spectroscopy(FTIR) and nuclear magnetic resonance(NMR) techniques,focusing on the effect of the PEO molecular weight on the spatial and dynamic heterogeneity.It is found,for the first time,that both the glass transition temperature(T_g) and activity energy(E_a) of the blends strongly depend on PEO molecular weight,and a common turning point,which separates the rapid and slow increasing regions,can be found.The interchain hydrogen bonding interactions,both determined by FTIR measurements and obtained from the Kwei equation,decrease with increasing PEO molecular weight,indicating a decrease of the componential miscibility.A series of parameters related to the microscopic spatial and dynamic heterogeneity,such as the activity energy, fragility,nonexponential factor and the size of cooperatively rearranging regions,are calculated from frequency dependency complex heat capacity measured using TOPEM.It is found that each of these parameters monotonically changes with increasing the PEO molecular weight during the glass transition process,demonstrating that hydrogen bonding interaction is the key factor in controlling the spatial and dynamic heterogeneity,thus the glass transition.NMR relaxation results reveal the existence of obvious phase separation large than 5 nm,implying that the cooperatively rearranging regions should be closely related to the interphase region between the two components.The above obtained origin and evolution of spatial and dynamic heterogeneity provide a new insight into the glass transition behavior of polymer blends.     

Miscibility evaluation of SPS/APS blend investigated from crystallization dynamics

The miscibility of crystalline syndiotactic polystyrene (SPS)/non-crystalline atactic polystyrene (APS) blend was estimated by the crystallization dynamics method, which evaluated the nucleation rate, the crystal growth rate and the surface free energy parameter. The melting temperature depression suggested that SPS/APS blends were the miscible system but not in molecular level. The relationship between the blend content and the chemical potential difference evaluated at a constant crystal growth rate showed a good linear relationship. These facts suggested that SPS/APS blends contained the concentration fluctuation with the size between few nm to less than 80 nm. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of Emulsifiers on Acrylate Latex Blends

The poly(methyl methacrylate/butyl acrylate/acrylic acid) [P(MMA/BA/AA)] and poly (styrene/butyl acrylate/acrylic acid) [P(St/BA/AA)] latexes were synthesized using the emulsifier octylphenol polyoxyethylene(10) ether (OP-10) and ammonium sulfate allyloxy nonylphenoxy poly(ethyleneoxy)(10) ether(DNS-86). The optimum amount of OP-10 and DNS-86 was 1.5% and 2.5% respectively. The P(MMA/BA/AA) and P(St/BA/AA) latex containing 1.5% OP-10 or 2.5% DNS-86 were blended pairwise. The performances of latex blends and parent latexes as a function of emulsifiers content in parent latexes were determined. The results indicated that the stability of latex blends is favorable, and particle size distribution was more uniform and thermal stability was improved after blending.